The telescopic mechanism and the tilting mechanism aim at adjusting back-and-forth position and tilt angle of a steering wheel to the easiest-to-manipulate position according to the driver's body form and taste.
The telescopic mechanism and the tilting mechanism are respectively provided with a column clamp which is clamped/unclamped for adjusting the steering wheel to back-and-forth position and a tilt head clamp which is also clamped/unclamped for adjusting tilt angle of the steering wheel. During these adjustments, the clamping condition of these column clamp and tilt head clamp is once cancelled and after back-and-forth position and tilt angle are adjusted under such condition, these are clamped again.
As a means for maintaining the clamping conditions of the column clamp and the tilt head clamp after back-and-forth position and tilt angle of the steering wheel are adjusted, each clamping device uses a spring. There has been disclosed in the British Patent No. 2 281 375 a steering column which enables adjustment of back-and-forth position and tilt angle of the steering wheel using a single control lever which can be manipulated without removing a hand from the steering wheel.
In the steering column disclosed in the British Patent, the control lever is always retreated to a retreat position away from the steering wheel because it is pulled with force of a tensile spring in view of preventing an accident that the driver's hand is in contact with the control lever during the driving. On the occasion of adjusting the steering wheel, if the control level is pulled with a hand toward the steering wheel, the control level is pulled toward the steering wheel against the tensile spring. Movement of this control lever is transmitted to the column clamp for back-and-forth position adjustment provided away from the control lever via a cable movable in a flexible tube. Accordingly, the column clamp is unclamped.
Moreover, with movement of this control lever, the tilt head clamp for adjusting tilt angle provided in the periphery of this control lever operates toward unclamping side against a compression spring and a plate spring. When the steering wheel is manipulated with both hands, back-and-forth position and tilt angle of the steering wheel are adjusted, and the control lever is freed from fingers under the condition that the control lever is maintained with the fingers, the control lever is returned to the retreat position with forces of the tensile spring and compression spring and the column clamp and tilt head clamp are clamped.
In the steering column, adjustment of the steering wheel must be conducted while the control lever is continuously left in the unclamping condition. Since a spring force increases with increase in displacement thereof, the maximum force is required at the end position of the unclamping side where the spring is displaced to the most extent. Therefore, manipulation ability becomes worse because the steering wheel must be adjusted while a large force for maintaining the unclamping condition is continuously applied to the control level.
Moreover, if a longer control lever is used to increase a lever ratio in order to reduce the force for operating the control lever, manipulations of switches provided in the periphery of steering wheel are impeded and in addition the longer control lever interferes with an instrument panel at the time of secondary collision. Accordingly, here rises a demerit that the space for allocating the control lever is restricted.